Brantley Gilbert and Jana Kramer Are Engaged

Country star Brantley Gilbert received the best gift ever in the form of an enthusiastic "Yes!" when girlfriend, One Tree Hill actress and country singer Jana Kramer, accepted his proposal of marriage in Nashville on Sunday, his 28th birthday.

"We could not be happier!" the couple tell PEOPLE exclusively in a statement from their rep. "We are so excited to share this special time with our loved ones and cannot wait to start the rest of our lives together."

Gilbert proposed in Nashville at the historic Ryman Auditorium Theater, which he rented out for the day. It is also the site of the former Grand Ole Opry stage, where iconic country couple Johnny Cash and June Carter met.

"I was so surprised!" admits Kramer, 29. "He asked my mom for permission before he proposed, which meant a lot to me."